DEAR SACHIN,

FOR SELECTION OF DOUBLE SCREW CONVEYOR,WE SHOULD

KNOW THE FOLLOWING:-

1) MATERIAL TO BE HANDLED

2) CAPACITY

3) MATERIAL CHARACTERSTICS

4) LENGTH OF SCREW CONVEYOR

THE FILLING FACTOR WILL BE SELECTED BASED ON THE MATERIAL

TO BE CONVEYED AND ITS CHARACTERSTICS ETC. OR IN OTHER WORDS HOW MUCH MATERIAL IS FILLED IN THE TROUGH.

THANKS ■

Dear Shri Sachin,

The selection of particular type of screw conveyor is a big subject and cannot be narrated here. Firstly, I would like to draw your attention to the following variants of the screw conveyor in context of the points you have referred.

- Regular pitch screw conveyor

- Regular pitch double type screw conveyor

- Short pitch screw conveyor

- Short pitch double flight screw conveyor

The above mentions only certain types with respect to conveying. Of course there are also different versions such ribbon flight, pedal flight, etc. for specific function, other than just conveying.

As for the use of particular type in context of pitch and number of flights, I can mention only certain hints as below about their functional characteristics.

- Shorter pitch imparts more powerful push to the material (wedge principal or tightening screw having less helix angle).

- Shorter pitch or double flight promotes more precise / steady flow.

- Shorter pitch and double flight reduces the material flush back (fluidic material).

- Shorter pitch reduces the agitation.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyors.

Author of Book : Belt Feeder Design and Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

You say that you wish to determine the design yourself yet are asking other to supply the information. I suggest that if you wish to understand the mechanics of screw equipment and of particuate solids. it would be better to start with the literature and develop an appreciation on fundamental grounds, rather than the opinion of others.

As RPD says, an ash conditioner is totally different from a screw conveyor and the process is essentially one of continuous mixing. If you work through a literature search on helical screws and continuous mixing, you should form a good idea of what is involved. It is no task for amateurs to design equipment of this type. Even with 'simple' screw conveyors, it has been pointed out that there are many variations of construction and duty. Conveying, dispensing, feeding, elevating and screw hopper dischargers have different functions, objectives and work on a various different operating principles. For example, there is no comparison between the mechanics an Archimedian conveyor and a static screw elevator as they operate on entirely different principles, although both employ a screw and a surrounding circular casing. I would recommend that you start with horizontal, controlled infeed, partially loaded screw conveyors, as described and backed with application data in the CEMA publications, and leave the awkward jobs to the specialists. There are enough disasters in the industry already, as the situation is not much improved from the Rand reposts of the 80's. ■

A screw type ash conditioner is at best a tempermental beast.

Even those who claim to know how to do it often end up making slightly wet dust or slurry.

Lyn's comments are a stern but fair warning! ■

Dear Sir,.

Thank you all of you for giving such information in detail.

Thanks & Regards,

Nikhil Mohite ■